Description:

Objective:

Effects of climate change on ecosystem structure and function are driven largely by environmental temperature, and because they often act as keystone species, large herbivores are likely to play an important role in responses of ecosystems to climate change. Nevertheless, little is known about how large herbivores respond behaviorally to spatiotemporal variability in the thermal environment, and how those responses influence individual fitness. The primary objectives of this research project are to: 1) evaluate direct and indirect influences of the thermal environment on behavior of North American elk occupying forested versus sagebrush steppe ecosystems; and 2) determine how differences in foraging and movement strategies relate to variability in fitness among elk.

Synopsis:

Large herbivores play important roles in the ecosystems they inhabit, and are capable of transporting both nutrients and contaminants great distances across landscapes. Consequently, understanding how these animals respond to climatic variability can provide insights into the potential effects of climate change on whole ecosystems. This project evaluates the causes and consequences of behavioral responses to climatic variability observed in North American elk occupying two different ecosystems.

Approach:

This research will utilize a biophysical model that combines detailed data on microclimate, topography, habitat, physiology, and morphology to produce spatiotemporally explicit estimates of metabolic expenditures by individual herbivores as they navigate a landscape. Model predictions will be combined with high-frequency location data from GPS collars and data on important fitness correlates such as birth mass of young and body condition at the onset of winter to evaluate relationships among the thermal environment, behavior, energy balance, and fitness of large herbivores. In addition, by evaluating these relationships for elk occupying a montane forest ecosystem versus an arid sagebrush-steppe ecosystem where temperatures and radiant heat loads are substantially higher, this analysis will provide important clues about how predicted increases in global temperatures are likely to influence large herbivores and the ecosystems they inhabit.

Expected Results:

Quantifying both direct and indirect effects of climate and associated weather patterns on animal behavior and physiology is necessary for understanding ecosystem responses to climate change and projecting future ecological trends. This research will provide a strong mechanistic foundation for understanding herbivore-mediated effects of climate change on ecosystems. For example, understanding the role of the thermal environment relative to other environmental factors (i.e., forage, risk of predation, topography, and human development) in influencing patterns of movement, behavior, and fitness of elk in an arid desert ecosystem will facilitate predictions of how increased temperatures resulting from climate change are likely to affect elk-ecosystem interactions in more classically occupied montane forests throughout the intermountain west. In addition, data collected for individual herbivores during this study will aid in explaining previously observed responses of herbivores to climate at the population level, which is of broad scientific value as a result of the important functional roles played by large herbivores in the ecosystems they occupy.

Potential to Further Environmental/Human Health Protection:

Large herbivores such as elk are extremely vagile, and are capable of transporting both nutrients and environmental contaminants great distances across landscapes. In addition, these animals often act as keystone species in the ecosystems they inhabit. This project will shed light on how individual herbivores respond to climatic variability, which will be critical for minimizing future negative effects of climate change on ecosystems occupied by large herbivores.

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.